454 
ACTINOPIEKYGII. 
Length of head with opercular apparatus considerably exceeding 
maximum depth of trunk, but equalling one third total length of 
fish to base of caudal fin. Vertebrae 14 in the abdominal, 16 in the 
caudal region. Anterior dorsal fin consisting of 10 slender spines, 
the posterior fin of about 20 rays, the first perhaps a spine ; anal 
fin with 2 or 3 feeble spines and about 20 articulated rays. 
Form. Sf Loc. Tertiary : Persia. 
P. 7130. Type specimen in compact limestone, partly obscured by 
oxide of manganese ; Shushter, Persia. The orbit is 
shown to he very large, and the mouth rather small, with 
minute, closely-set teeth. The oporculuin is rounded, and 
there are 7 branchiostegal rays. The pectoral fins aie 
small and low on the flank; the pelvic fins, with one 
slender spine and 5 articulated rays, are inserted slightly 
further back. The forked tail is well shown. There 
are no indications of scales. 
Presented by Alfred Holland, Esq., l^ll- 
Genus THYNNUS, Cuvier. 
[Regno Animal, vol. ii. 1817, p. 313.] 
Syn. Orcynus, G. Cuvier, ibid. 1817, p. 314. 
Trunk very robust and elongate-fusiform ; slender caudal 
pedicle, with strong median lateral keel formed by bony ridge on 
vertebral centra. Median pair of fossae for anterior extension of 
lateral muscles of trunk produced forwards over frontal bones and 
separated by median frontal ridge continuing the large supra- 
occipital crest ; lateral pair of fossae also producod half-way over 
frontals. Teeth small and conical, and in single series on margin 
of jaws, minute and clustered on vomer and palatines. Vertebrae 
about 40 in number, the centra constricted, with two lateral pit 8 
separated by a longitudinal ridge ; all haemal arches simple- 
Pectoral fins elongate, hut not extending boyond origin of anal , 
pelvic fins small ; dorsal fins scarcely separated, the anterior con- 
sisting of 12 to 15 spines; posterior dorsal and anal fins small hut 
elevated, similar and opposite, followed by 8 to 12 detached finlets , 
caudal fin deeply forked, with slender lobes. Scales very small, 
Uniformly covering the trunk, except in the pectoral region, where 
they are somewhat enlarged and compacted. 
The typical existing species is pelagic and attains gigantic 
proportions. 
